\definecolor{myblue}{cmyk}{.9932,.3041,0,.4196}
% \def\firstcircle{(0,0) circle (1.5cm)}
% \def\secondcircle{(0:2cm) circle (1.5cm)}

\tikzset{filled/.style={fill=myblue, fill opacity=0.5, draw=black},
    outline/.style={draw=circle edge, thick}}
    
\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

\everymath\expandafter{\the\everymath \color{myblue}}
\everydisplay\expandafter{\the\everydisplay \color{myblue}}

\renewcommand{\baselinestretch}{.8}
\pagestyle{empty}

\global\mdfdefinestyle{header}{%
linecolor=gray,linewidth=1pt,%
leftmargin=0mm,rightmargin=0mm,skipbelow=0mm,skipabove=0mm,
}

\renewcommand{\dot}[1]{
  \accentset{\mbox{\bfseries .}}{#1}}

\newcommand{\header}{
\begin{mdframed}[style=header]
\footnotesize
\sffamily
Classical~Mechanics~Cheat~Sheet\\
Xiaoye~Wu,~Page~\thepage~of~2\\
\textit{\email{xiaoyewu@ucm.es}}
\end{mdframed}
}

\makeatletter % Author: https://tex.stackexchange.com/questions/218587/how-to-set-one-header-for-each-page-using-multicols
\renewcommand{\section}{\@startsection{section}{1}{0mm}%
                                {.2ex}%
                                {.2ex}%x
                                {\color{myblue}\sffamily\small\bfseries}}
\renewcommand{\subsection}{\@startsection{subsection}{1}{0mm}%
                                {.2ex}%
                                {.2ex}%x
                                {\sffamily\bfseries}}
\makeatother
\setlength{\parindent}{0pt}

\def\scaleint#1{\vcenter{\hbox{\scaleto[3ex]{\displaystyle\int}{#1}}}}